1. Technical Field
The present invention relates to a suspension wire for compensating for hand vibration and an image photographing device having the same, and more particularly, to a suspension wire for compensating for hand vibration in which a shape and a supporting structure of the suspension wire supporting an optical unit are changed to prevent permanent deformation or fracture of the suspension wire due to external impact, and an image photographing device having the same.
2. Description of the Related Art
Recently, use of a subminiature camera module for a mobile has gradually increased in a mobile device such as a mobile phone, a notebook, a tablet PC, or the like. The demand of customers for the subminiature camera used in the mobile device and having a high pixel of five million pixels or more and a multi-function such as a zoom function, an auto focus (AF) function, and the like has increased.
Generally, a camera module used in the mobile device may be configured to include an optical system having a lens, a lens moving unit moving the optical system in an optical axis direction to adjust a focus, and an image sensor photographing light input through the optical system to convert the photographed light into an image signal.
As the number of pixels of the camera module is increased, the size of the pixel becomes small and the receiving sensitivity of the light photographed in the image sensor becomes sensitive, and the image photographed in the image sensor is out of focus even with small hand vibration when operating a shutter of the camera or the mobile device, such that image quality is deteriorated. Therefore, it is impossible to obtain a sharp photograph.
The deterioration of the image quality due to the hand vibration is generated because the light passing through the lens of the optical system is out of the optical axis of the lens. Therefore, in order to prevent the deterioration of the image quality due to the hand vibration, the lens is moved in directions perpendicular to the optical axis to coincide the optical axis of the lens with an incident pass of the light or the image sensor is moved in directions perpendicular to the optical axis to coincide the optical axis with the incident pass of the light received in the image sensor, thereby compensating for the hand vibration.
That is, the lens or the image sensor is relatively displaced in the directions perpendicular to the optical axis, respectively, thereby making it possible to compensate for the hand vibration.
In a scheme in which the lens or the image sensor is relatively displaced to compensate for the hand vibration, generally, a two-axis guide supporting the lens in a T shape or an L shape is mounted, such that the lens is moved in the relative direction of moving displacement generated due to the hand vibration while being moved in directions perpendicular to the optical axis along the two-axis guide, thereby compensating for the hand vibration.
Here, when the lens is moved along the two-axis guide, compensation performance may be deteriorated due to the friction between the two-axis guide and the lens, and when the two-axis guide and the lens are moved or the two-axis guide is moved, noise or foreign materials may occur due to the friction with other components.
In addition, since the two-axis guide supports the periphery of the lens, the size of the camera module cannot but be enlarged by a space in which the two-axis guide is mounted.
Meanwhile, in order to reduce noise or the foreign material, a scheme of moving the optical unit in directions perpendicular to the optical axis in a state in which the optical unit is supported and floated through a suspension wire may be used. Here, the optical unit is moved in the relative direction of moving displacement generated due to the hand vibration by electromagnetic force in a state in which it is supported by the suspension wire, thereby compensating for the hand vibration.
In the hand vibration compensation device in the above-mentioned scheme, friction between the optical unit and other components does not occur during the movement of the optical unit, such that noise and foreign material due to the friction do not occur, thereby making it possible to minimize performance deterioration.
However, when an image photographing device is mounted in an actual mobile device and has external impact such as dropping, etc., applied thereto, compressive stress or tensile stress is applied to the suspension wire supporting the optical unit. When these stresses exceed yield stress of the suspension wire itself, deformation of the suspension wire such as warpage, fracture, or the like, occurs.
That is, when one or more axis of the suspension wire supporting the optical unit is deformed, a hand vibration compensation function may be deteriorated or slanted, and when the suspension wire is fractured, the hand vibration compensation function itself may become impossible.
In order to prevent these problems, a diameter of the suspension wire may be enlarged to increase the yield stress thereof. However, in the case in which the diameter of the suspension wire is enlarged, spring stiffness increases in directions perpendicular to an optical axis, such that moving performance of the hand vibration compensation may be deteriorated and a size of a moving member may be increased, thereby causing an increase in the entire size of the image photographic device having the hand vibration compensation function.